1. Field of the Invention
The present invention relates to a method of purifying photographic materials and more particularly to a method of purifying dispersions or emulsions for photographic materials by continuously gelling the dispersions or emulsions under cooling while forming them into thin films and thereafter washing said thin films with water. This invention further relates to an apparatus for conducting the above method.
2. Description of the Prior Art
In order to remove impurities from a dispersion or emulsion for photographic material mainly consisting of gelatin and capable of being gelled by cooling, such as, gelatino silver halide emulsions, matting-agent-containing gelatin emulsions, coupler-containing gelatin emulsions, dye-containing gelatin emulsions for filter layers, and the like, in particular, for desalting gelatino silver halide emulsions, there has usually been employed a method wherein the dispersion or emulsion is gelled by cooling, cut into fine noodle like strands, and washed with cold water. The dispersion or emulsion however must be sufficiently gelled by cooling in order to cut it into the fine strands prior to water washing and hence the cutting operation must be conducted separately from the cooling operation, which requires a long period of time for finishing the purification as well as for installations. Moreover, in the above method, the more finely the gelled dispersion or emulsion is cut, the more effectively and rapidly the water washing can be accomplished. However, if the gel is cut into finer pieces, the sufficient recovery of the finer pieces after washing becomes difficult, resulting in large loss thereof. Accordingly, there is a limit in the degree of fineness to which the strands can be cut which makes it impossible to increase sufficiently the washing efficiency. Furthermore, the conventional method is accompanied with such disadvantages that it is difficult to conduct the purification steps continuously through cooling, cutting and washing and it is difficult to obtain a dispersion or emulsion having constant and uniform qualities.
Therefore, an object of this invention is to provide a method and apparatus of purifying photographic materials as mentioned above capable of easily and continuously purifying gellable dispersions or emulsions for photographic materials.
Another object of the invention is to provide a method and apparatus for purifying gellable dispersions or emulsions for photographic materials in which water washing can be rapidly accomplished in a short period of time.
A further object of this invention is to provide a method and apparatus for purifying photographic materials which is capable of obtaining purified photographic dispersions or emulsions having consistently uniform qualities with reduced loss.